Garden Talk: February 9, 2012

From NGA Editors

Island Time at the 2012 Philadelphia International Flower Show

Although enthusiasm is a job requirement when overseeing the world's largest indoor flower show, show designer Sam Lemheney practically levitates when talking about Hawaii: Islands of Aloha. ″It will feel like you're at the Flower Show for the very first time,″ he says, looking over design sketches for the 2012 Philadelphia International Flower Show.

What will you see this year? Massive specimen orchids. Rare tropical plants. High-energy performances. And, most importantly, the aloha spirit wherever you go. High-definition projection artistry will create a virtual wave of water against a brilliant bank of flowers, including white anthuriums and orchids. Sam says this is the perfect way to enter the ″tropical immersion area -- a thick, lush rainforest garden filled with even more orchids, foliage, and ferns suspended overhead.″ Waldor Orchids of New Jersey will supply the exotic specimens.

Pele -- Hawaiian goddess of fire, wind, lightning, and volcanoes -- will have her own garden, too. ″There will be a 25-foot-tall waterfall crashing down into a 30-foot-wide pool -- it's the largest waterfall we've ever attempted,″ Sam says.

Massive displays in the Showcase Garden category will highlight cultural and horticultural aspects of Hawaii. This includes the American Institute of Floral Designers' floral interpretation of the hula and leis; Stoney Bank Nurseries' celebration of island cuisine; Burke Brothers Landscape Contractors' surfer's hangout; and an out-of-this-world rock garden created by Michael Petrie's Handmade Gardens.

Visit the Philadelphia International Flower Show, March 4 - 11, and you, too, can share Sam's enthusiasm for what is sure to be an amazing experience. ″It's completely different from any other year,″ says Sam. ″You'll just have to see it to believe it.″

Want to experience the Flower Show firsthand? NGA fans are invited to take advantage of the Flower Show value packages, the best ways for duos, foursomes, and families to see the Show. For additional information or to purchase tickets, visit The Flower Show. All proceeds from the Flower Show support the Pennsylvania Horticultural Society and its acclaimed urban greening programs, including City Harvest.

New Hardiness Zone Map

The USDA has released the long-awaited, updated version of its hardiness zone map, giving some areas of the country new zone designations. The new 2012 map is based on temperature data from the thirty year period 1976- 2005, so more recent temperature trends are incorporated into its zone listings. It is also based on data from even more weather stations than the previous map, enhancing its accuracy.

The hardiness zone map is divided into zones based on the average annual extreme minimum temperature in a particular area -- in other words, the coldest temperature, on average, that occurs over the winter. There are now 13 zones, (two new ones have just been added) further subdivided into ″a″ and ″b″ categories. Each zone represents a temperature range of ten degrees; each ″a″ or ″b″ subdivision five degrees. The lower the number, the colder the zone; and ″a″ is colder than ″b.″

While a few areas were moved to slightly cooler zones, the majority of the changes on the new map reflect a shift to warmer zones, with the zone boundary generally moving up by a half zone, or a five degree change. While many of these changes are due to changes in climate patterns, some are a result of the increased regional accuracy of the map to better reflect the influence of local geography, like changes in elevation or nearness to a body of water, on temperature extremes.

One of the handiest aspects of the new map is its interactive feature that lets you find your zone by typing in your zip code on the map website. You can also zoom in on the map of your state to see the zone boundaries in detail and download and print maps of various sizes and resolutions.

Does this new zone map show that the climate is warming? Taken by itself, the map is not designed to answer this question. Remember that what the map shows is the average lowest yearly temperature over the last thirty years, which has indeed moved higher in many areas in recent decades. But it doesn't provide information about winter temperatures apart from these extremes, or about summer temperatures or changes in any other climatic parameters. Figuring out if and how much the climate is warming is based on overall climate trends that take lots of factors in account, of which the average of extreme winter lows shown by the zone map is just one.

Lyme Disease on the Move

A new research study by the Yale School of Public Health shows that Lyme disease is on the move. A map showing the areas of highest risk for Lyme disease infection in the U.S. is part of the study published in the February issue of the Journal of Tropical Medicine and Hygiene.

Gardeners, hikers, or anyone who spends time outdoors are at particular risk of this tick-borne ailment. It can usually be treated readily with antibiotics if diagnosed early, but its sometimes vague symptoms can make this difficult. Infections that are not treated promptly can lead to arthritis, meningitis, and a host of other complications. Researchers hope the new map will help doctors and the public increase early diagnoses with a better awareness of the risks of infection in different locations.

Based on data collected from 2004 to 2007, the study shows the Northeast from Maine to northern Virginia continuing to be a high-risk region, with the Upper Midwest, including most of Wisconsin, northern Minnesota, and parts of northern Illinois classified as high risk as well. Areas of ″emerging risk″ are noted, including the Illinois-Indiana border, the New York-Vermont border, southwestern Michigan, and eastern North Dakota. It is likely that risk profiles in these transitional areas have increased since data was collected in 2007.

A great new tool to help you figure out not only the abundance of the ticks that spread Lyme disease in a particular location, but also how to identify and remove them, is a free iphone app developed by the laboratory of Dr. Durland Fish at the Yale School of Public Health. This app figures out your location and tells you how common the deer ticks that transmit the disease are in that area.

If you find a tick on yourself, your pet, or in the wild, you can watch a video showing how to remove it safely and then identify it by placing it on your phone screen, where you can match it to images of various tick species. (Not all kinds of ticks are Lyme disease vectors.) There is even a section that lets you figure out how long the tick has been attached, which is important since the longer it's attached, the greater the likelihood of disease transmission. Even if you live in an area where Lyme disease is not currently a threat, this app can be helpful when you travel or vacation in other parts of the country.

To read more about the map and research on areas of Lyme disease risk, go to, go to: Burlington Free Press. To find out more about the Lyme Disease iphone app, go to, go to: itunes.

Changing the Rules Because of Oak Wilt

For years gardeners were counseled to paint over tree wounds and pruning cuts to seal them. This seemed like a logical course of action, like putting a bandage over a scraped knee. It wasn't until the 1970s that this practice was assessed scientifically, when it was found that sealing tree wounds didn't promote healing and, in some cases, even increased the chances of decay. Gardeners were then advised to leave pruning cuts and other tree wounds unsealed. That advice still holds, but now with one important exception -- when pruning oaks in areas where oak wilt is a threat.

Oak wilt is one of the most serious tree diseases in the eastern U.S. A fungal disease first identified in 1944, it attacks many species of oaks and kills thousands of trees every year. Researchers are not sure if the disease-causing fungus is native or imported, but either way, it's an aggressive pathogen. Trees in the red-black oak group are especially susceptible, but those in the white and live oak groups are also at risk.

The disease is currently found mainly in the Midwest and Texas, but occurs as far east as western Pennsylvania and eastern Virginia, and has even been found in pockets in North and South Carolina (areas in red on the map). The most common way for the oak wilt fungus to infect trees is through wounds, and it's thought that the increase in home construction in oak woods, with the resulting increase in damage to trees, has added to the spread of the disease in recent years.

The oak wilt fungus forms what are called spore mats on infected trees. These mats emit an odor that attracts certain species of sap beetles, which then pick up spores on their bodies. If these beetles then visit a fresh wound leaking sap on an uninfected tree, they can deposit spores and spread the disease. And this is why the recommendation on using wound dressings on oaks has changed. Sealing cuts and wounds will make them less likely to attract the beetles that spread the disease.

The most favorable time for new infections to get started varies regionally. Spring and early summer are the time when spore mats are formed and beetles are flying, usually from about April 15 to July 1 in the Great Lakes region, with the period gradually lengthening as you go southward, extending from February through June in Texas. So it's important to avoid pruning trees during the critical period, if possible. In northern areas, pruning cuts made anytime except during the winter dormant season should be coated immediately with latex paint to seal them. From Missouri south to Texas, cuts made at any time of the year should be sealed.

If you are involved in a construction project or other activity that could potentially wound trees, do your best to protect plants from damage. And watch out for weed whacker and lawn mower damage to tree trunks!

For more information on diagnosing, treating, and preventing oak wilt and where it is a threat, go to: Forest Health Protection.